The embodiments described herein relate generally to electric vehicles and, more specifically, to methods and systems for charging a vehicle that includes an electrochemical energy storage device.
In response to both increasing fuel costs related to the use of conventional combustion engine vehicles and heightened environmental concerns, including air pollution, the use of electric and hybrid vehicles has increased. As a result, energy demand will likely increase in the form of electrical energy used to charge batteries or other energy storage devices used in such vehicles. Electric vehicles, or vehicles that include an electrochemical energy storage device, are defined herein as vehicles that derive some portion of the power used to propel the vehicle from an energy storage device, for example, from batteries. Electric vehicles may include, but are not limited to, vehicles that rely solely on power stored in batteries to drive an electric motor that propels the vehicle (e.g., a traction motor), vehicles that include batteries for storing power used to drive a traction motor and also include an internal combustion engine that drives a generator used to recharge the batteries, and vehicles that include a combination of electric and fossil fuel powered components (e.g., hybrid vehicles). Examples of hybrid vehicles include parallel hybrid vehicles, series hybrid vehicles, and mixed hybrid vehicles. In a parallel hybrid vehicle, an internal combustion engine and an electric machine are mechanically coupled with a traction system. In a series hybrid vehicle, an internal combustion engine and an electric machine are mechanically coupled with a generator and the traction system. Furthermore, a mixed hybrid vehicle is a combination of a parallel and series hybrid vehicle, where the internal combustion engine may be mechanically coupled to the traction system.
Currently, multiple charging levels are available for charging batteries included within an electric vehicle. Examples of different charging levels are described in the Society of Automotive Engineers (SAE) Standard J1772, SAE Electric Vehicle and Plug in Hybrid Electric Vehicle Conductive Charge Coupler. A first and a second charging level may be referred to as slow alternating current (AC) charging. To charge using the first charging level, the electric vehicle is coupled via an AC to AC connector to a vehicle charging station, or to a standard residential electrical outlet, which provides, in the example of the United States of America, 120 volts of alternating current (VAC) at approximately 15-20 amperes. Charging at the first charging level may require 8 to 24 hours to fully charge an electric vehicle. To charge using the second charging level, the electric vehicle is coupled via an AC to AC connector to a vehicle charging station that provides, for example, 240 VAC at approximately 30-32 amperes. The higher power of the second charging level facilitates a quicker charging cycle for the electric vehicle than provided by the standard electrical outlet. For example, charging at the second charging level may require 4 to 10 hours to fully charge the electric vehicle. Typically, the electric vehicle includes an AC to direct current (DC) converter dedicated only to charging. The AC to DC converter provides DC power to the battery for charging.
Additional charging levels may be referred to as “fast charging” levels. Fast charging levels typically apply DC power to the electric vehicle. For example, a fast charging system may apply a DC power directly to a DC bus within the electric vehicle. More specifically, an AC power is received at a vehicle charging station at a high voltage, for example, 480 VAC in the United States of America or 690 VAC in Europe. The vehicle charging station includes an AC to DC converter and the DC power output of the AC to DC converter is provided to the electric vehicle via a DC cable. The DC power provided to the electric vehicle may be in the range of 60 kilowatts (kW) to 150 kW and allow the electric vehicle to reach a 50% charge level in approximately 10-15 minutes.